Distinct and common pathways of expectancy and recollection of emotional visual stimuli – a high resolution fMRI Study at 7 Tesla

Background: Vulnerability of the substantia nigra dopaminergic neurons in Parkinson's disease is associated with ferric overload, leading to neurodegeneration with cognitive and motor decline. Here, we quantify iron and neuromelanin-related markers in vivo using ultra-high field 7-Tesla MRI, and examine the clinical correlates of these imaging assessments. Methods: Twenty-five people with mild-to-moderate Parkinson's disease and twenty-six healthy controls underwent high-resolution imaging at 7-Tesla with a T2*-weighted sequence (measuring susceptibility-χ and R2*, sensitive to iron) and a magnetization transfer-weighted sequence (MT-w, sensitive to neuromelanin). From an independent control group (N=29), we created study-specific regions-of-interest for five neuromelanin- and/or iron-rich subregions within the substantia nigra. Mean R2*, susceptibility-χ and their ratio, as well as the MT-w contrast-to-noise ratio (MT-CNR) were extracted from these regions and compared between groups. We then tested the relationships between these imaging metrics and clinical severity. Results: People with Parkinson's disease showed a significant ~50% reduction in MT-CNR compared to healthy controls. They also showed a 1.2-fold increase in ferric iron loading (elevation of the ΔR2*/Δχ ratio from 0.19±0.058ms/ppm to 0.22±0.059ms/ppm) in an area of the substantia nigra identified as having both high neuromelanin and susceptibility MRI signal in healthy controls. In this region, the ferric-to-ferrous iron loading was associated with disease duration (β=0.0072, pFDR=0.048) and cognitive impairment (β=-0.0115, pFDR=0.048). Conclusions: T2*-weighted and MT-weighted high-resolution 7T imaging markers identified neurochemical consequences of Parkinson's disease, in overlapping but not-identical regions. These changes correlated with non-motor symptoms.

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Perfusion-based high-resolution functional imaging in the human brain at 7 Tesla

Magnetic Resonance in Medicine ◽

10.1002/mrm.10154 ◽

2002 ◽

Vol 47 (5) ◽

pp. 903-911 ◽

Cited By ~ 88

Author(s):

Josef Pfeuffer ◽

Gregor Adriany ◽

Amir Shmuel ◽

Essa Yacoub ◽

Pierre-Francois Van De Moortele ◽

...

Keyword(s):

High Resolution ◽

Human Brain ◽

Functional Imaging ◽

7 Tesla

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Abstract 295: Magnetic Resonance Imaging Characterization of Peripheral Arterial Chronic Total Occlusions With MicroCT and Histologic Validation

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.35.suppl_1.295 ◽

2015 ◽

Vol 35 (suppl_1) ◽

Author(s):

Trisha Roy ◽

Garry Liu ◽

Xiuling Qi ◽

Andrew Dueck ◽

Graham Wright

Keyword(s):

High Resolution ◽

Imaging Techniques ◽

Calcium Sensitivity ◽

7 Tesla ◽

Chronic Total Occlusions ◽

Difference Image ◽

Surgical Bypass ◽

Phase Map ◽

Peripheral Arterial ◽

Difference Images

Objectives: Guidelines recommend surgical bypass for peripheral chronic total occlusions (CTOs). Endovascular revascularization, however, offers improved morbidity and shorter length of hospitalization. Not all lesions are amenable to this technique but predicting crossability is difficult due to limitations in characterizing CTOs with current imaging techniques. This study demonstrates the ability of MRI to characterize peripheral CTO components with microCT and histologic validation. Methods: MRI was performed on 15 excised human peripheral arterial CTO segments from 4 patients. Each sample was imaged at 7 Tesla at high resolution (75μm3 voxels) to produce T2- and T2*-maps using ultrashort echo (UTE) sequences with echo times: {20μs, 500μs, 1ms}. A T2* difference image was produced by subtracting the UTE images and a phase map was constructed. The T2, UTE 20μs and T2* difference images were used together to differentiate CTO components. MicroCT and histology were used to validate regions of interest (ROIs). Results: 3 independent reviewers identified 47 ROIs. There was excellent agreement between MRI and microCT for calcium (sensitivity 87%, specificity 99%). There was also good agreement between MRI and histology for adipose tissue (100%, 100%), soft tissue (97%, 97%), thrombus (78%, 100%), collagen (83%, 94%) and open lumen (95%, 98%). Conclusions: These results demonstrate the potential of high-resolution T2 and T2* imaging using UTE, to characterize lesion components in human peripheral CTOs. Further work is required to better differentiate thrombus from collagen. This study provides the foundation for future studies in determining the lesion crossability in CTOs.

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